All multicellular organisms harbor an unimaginably large number of microorganisms in and on their bodies. The microbiome, i.e. the totality of these microbes, forms a functional, symbiotic unit with the host organism. From supporting nutrient uptake to protecting against pathogens, microorganisms perform vital tasks for the host. On the contrary, disturbances of the microbiome can cause various serious diseases, including inflammatory bowel disease.